DE102009003545A1 - A method of preparing a blend for a PTFE membrane with metal oxides and related compositions - Google Patents

Abstract

A process for preparing a blend used in the manufacture of a polytetrafluoroethylene (PTFE) membrane which includes metal oxide (s). The mixture includes PTFE resin, a lubricant and a metal oxide. The mixture can be further processed to form a PTFE membrane.

Description

BACKGROUND OF THE INVENTION

embodiments The present invention relates generally to manufacturing a membrane of expanded polytetrafluoroethylene (ePTFE), the Contains metal oxide (s).

Materials, which include polytetrafluoroethylene (PTFE) are in the Known in the art. PTFE has several well-founded ones Applications, including, e.g. For example, applications that require lubricity (eg bearings, bushes, etc.) and applications that are porous Require membrane. These membrane applications can, for. B., filtration, venting and / or diffusion / barrier applications lock in. Filtration can use discs or foils.

Additive-containing PTFE products are known. See, eg. B., U.S. Patent 5,697,390 Garrison et al .; 5,827,327 McHaney et al .; 6,120,532 of gold color and 6,270,707 by Hori et al.

BRIEF DESCRIPTION OF THE INVENTION

A Embodiment of the present invention is a method for producing a polytetrafluoroethylene membrane, the metal oxide (s) includes. The method may include the steps of: (a) mixing a weight-bearing polytetrafluoroethylene resin, one, a weighted lubricant and one having a weight Metal oxides, wherein the weight of the lubricant between 15 and 25 percent of the weight of the polytetrafluoroethylene resin and the weight of the metal oxide up to 10 weight percent of the weight of the polytetrafluoroethylene resin, and wherein the metal oxide has at least one dimension of less than 100 nm; (b) forming one, a mixture of the polytetrafluoroethylene resin, the lubricant and the metal oxide-containing preform; (c) extruding the preform for forming a tape having a thickness between 1 and 100 mils; (d) calendering the ribbon to facilitate evaporation of the ribbon lubricant; (e) tension the tape by biaxially stretching in a first direction and in a second direction, the vertical to the first direction to form a membrane, and (f) sintering the membrane at a temperature between 400 ° F and 750 ° F for a period of between 1 and 120 seconds, with the Membrane after sintering has a thickness between 0.05 and 20 mil.

A Embodiment of the present invention is a method for introducing a metal oxide into a mixture comprising Polytetrafluoroethylene resin and a lubricant. The procedure can the steps include: (a) mixing the polytetrafluoroethylene resin with the lubricant in a V-mixer for a period of time between 1 and 60 minutes to add a resin / lubricant mixture form; (b) drawing in the resin / lubricant mixture for a period of between 1 and 120 hours, and (c) mixing the resin-lubricant mixture with the metal oxide in a V-mixer for a period of time between 1 and 60 minutes, with a weight of the lubricant between 15 and 25 percent of a weight of the polytetrafluoroethylene resin and a weight of the metal oxide up to 10 percent of the weight of the polytetrafluoroethylene resin, and wherein the metal oxide has at least one dimension of less than 100 nm.

One embodiment of the present invention is a composition comprising: a polytetrafluoroethylene resin, a lubricant comprising an isoparaffinic solvent, and a metal oxide wherein a weight of the lubricant comprises between 15 and 25 percent by weight of the polytetrafluoroethylene resin and a weight of the metal oxide of up to 10 percent of the weight Weight of the polytetrafluoroethylene resin, and wherein the metal oxide at least a dimension of less than 100 nm and a specific. Surface of more than 50 m ² / g.

DETAILED DESCRIPTION THE INVENTION

Certain Aspects of the present invention may be related be set to extrude polytetrafluoroethylene (PTFE), which includes metal oxide nano-composite, to tape and then converting the extruded PTFE tape into a membrane biaxial stretching.

In certain embodiments, a combination of PTFE and metal oxide (s) (e.g., nano-composites) may be prepared by dispersing metal oxide (s) such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), aluminum oxides (Al ₂ O ₃ ), Magnesium oxide (MgO), silver oxide (AgO) and other nano-materials are prepared in a PTFE resin-containing mixture. The PTFE composite may then be extruded into ribbon and converted to a membrane by biaxial stretching.

Suitable metal oxides may, for. B., copper (I) oxide (Cu ₂ O); Silver (I) oxide (Ag ₂ O); Thallium oxide (Ti ₂ O); Sodium oxide (Na ₂ O); Aluminum oxide (AlO); Barium oxide (BaO); Beryllium oxide (BeO); Cadmium oxide (CdO); Calcium oxide (CaO); Cobalt (II) oxide (CoO); Cupric oxide (CuO); Ferric oxide (FeO); Magnesium oxide (MgO); Mercury (II) oxide (HgO); Nickel (II) oxide (NiO); Palladium (II) oxide (PdO); Silver (II) oxide (AgO); Strontium oxide (SrO); Stannous oxide (SnO); Titanium (II) oxide (TiO); Vanadium (II) oxide (VO); Zinc oxide (ZnO); Alumina (Al ₂ O ₃ ); Antimony trioxide (Sb ₂ O ₃ ); Bismuth trioxide (Bi ₂ O ₃ ); Chromium (III) oxide (Cr ₂ O ₃ ); Erbium (III) oxide (Er ₂ O ₃ ); Gadolinium (III) oxide (Gd ₂ O ₃ ); Gallium (III) oxide (Ga ₂ O ₃ ); Holmium (III) oxide (Ho ₂ O ₃ ); Indium (III) oxide (In ₂ O ₃ ); Ferric oxide (Fe ₂ O ₃ ); Lanthanum (III) oxide (La ₂ O ₃ ); Lutetium (III) oxide (Lu ₂ O ₃ ); Nickel (III) oxide (Ni ₂ O ₃ ); Promethium (III) oxide (Pm ₂ O ₃ ); Rhodium (III) oxide (Rh ₂ O ₃ ); Samarium (III) oxide (Sm ₂ O ₃ ); Scandium (III) oxide (Sc ₂ O ₃ ); Terbium (III) oxide (Tb ₂ O ₃ ); Thallium (III) oxide (Tl ₂ O ₃ ); Thulium (III) oxide (Tm ₂ O ₃ ); Titanium (III) oxide (Ti ₂ O ₃ ); Tungsten (III) oxide (W ₂ O ₃ ); Vanadium (III) oxide (V ₂ O ₃ ); Ytterbium (III) oxide (Yb ₂ O ₃ ); Yttrium (III) oxide (Y ₂ O ₃ ); Cerium (IV) oxide (CeO ₂ ); Chromium (IV) oxides (CrO ₂ ); Germanium dioxide (GeO ₂ ); Hafnium (IV) oxide (HfO ₂ ); Manganese (IV) oxide (MnO ₂ ); Plutonium dioxide (PuO ₂ ); Ruthenium (IV) oxide (RuO ₂ ); Thorium dioxides (ThO ₂ ); Tin dioxide (SnO ₂ ); Titanium dioxide (TiO ₂ ); Tungsten (IV) oxide (WO ₂ ); Vanadium (IV) oxide (VO ₂ ); Zirconia (ZrO ₂ ); Antimony pentoxide (Sb ₂ O ₅ ); Tantalum pentoxide (Ta ₂ O ₅ ); Vanadium (V) oxide (V ₂ O ₅ ); Chromium trioxide (CrO ₃ ); Molybdenum (VI) oxide (MoO ₃ ); Rhenium trioxide (ReO ₃ ); Tungsten trioxide (WO ₃ ); Manganese (VII) oxide (Mn ₂ O ₇ ); Rhenium (VII) oxide (Re ₂ O ₇ ); Osmium tetraoxide (OsO ₄ ); Ruthenium tetraoxide (RuO ₄ ); and permutations and combinations of such (and other) metal oxides.

A membrane containing metal oxide (s) may have a high porosity / surface area and may, at least in some cases, be used in the decontamination of chemical and / or biological agents. So can, for. B., silver oxide and magnesium oxide antimicrobial properties. In another example, silver oxide (converted to Ag ⁺ when in contact with water, including, for example, body fluids such as perspiration) can kill microorganisms.

In In some cases, the metal oxide nanoparticles Impart properties such as increased abrasion resistance, increased tensile strength, increased tensile modulus, etc., the mechanical stability and / or durability of the Can promote membrane.

In certain embodiments, e.g. For example, the metal oxide (s) may be small particles having at least one dimension of less than 100 nm. Preferably, the metal oxide (s) have at least a dimension of less than 50 nm, and more preferably, the particles have at least a dimension of less than 30 nm. Suitable nanoparticles may have a high surface to volume (or mass) ratio. So can, for. B., suitable nanoparticles have a specific surface area of more than 10 m ² / g, more than 50 m ² / g or more than 90 m ² / g. In some embodiments, the specific surface area may be about 100 m ² / g. A suitable inorganic porous material may include zinc oxide nanopowder available from Aldrich Chemical Co.

In preferred embodiments relate to certain aspects the present invention to a method for producing a a metal oxide-containing PTFE membrane. In general, you can the stages include one or more of the following stages: (1) Mix PTFE resin with a lubricant, then let it retract the resin / lubricant mixture; (2) Mixing the resin / lubricant mixture with a metal oxide such as zinc oxide nanopowder; (3) preforming the wet mixture to a bar or billet; (4) Extrude the mix to band; (5) calendering the tape; (6) biaxial Stretching the ribbon to form a membrane; and (7) sintering the ribbon Membrane for stabilizing its microstructure.

by virtue of the use of a lubricant after the application of heat removed from the extrudate, this process can generally be described as a "wet process" and not as a "dry process" (which is generally based on non-friction Air mixing in a non-shear environment) become.

In an exemplary embodiment, a suitable PTFE resin comprises Dupont ^Teflon® PTFE 601A available from EI du Pont de Nemours and Co. Other PTFE resins may include Daikin F107, Dupont 603A and / or Dupont 60A. In an exemplary embodiment, a suitable lubricant includes a hydrocarbon-based liquid such as the isoparaffinic solvents sold under the tradename Isopar by Exxon Mobil Chemical Co. A preferred lubricant may include Isopar K, Isopar M and / or Isopar G. The PTFE resin powder may be mixed with the lubricant in a V-blender for 1 to 60 minutes (preferably about 30 minutes), e.g. B. until the mixture is suitably homogeneous. In certain embodiments, the weight percent of the lubricant may range between 15 and 25% (and all sub-ranges therebetween) of the weight of the resin. These weight percentages, commonly known as the "lubricant (lube) rate", may vary, for example, depending on the specific processing parameters of the equipment used in the extrusion ming.

The Retraction takes place after mixing and the resin / lubricant mixture can last for 18 hours at a temperature of 90 ° F being held. In certain embodiments, the Temperature higher (eg 200 ° F) or lower (eg 40 ° F) and the time may be shorter (eg 1 Hour) or longer (eg 120 hours). In other Embodiments may include "wicking" optionally done.

The retracted resin / lubricant mixture can then with metal oxide using a V-mixer, z. B. at ambient temperature for 1 to 60 minutes, preferably between 15 and 30 minutes, mixed become. In some embodiments, the metal oxide comprises up to 10% by weight of the PTFE resin. In other embodiments For example, the metal oxide comprises up to 5% by weight of the PTFE resin. In still In other embodiments, the metal oxide comprises up to 3 wt .-% of the PTFE resin.

In In certain embodiments, the lubricant may be dispersing of the metal oxide (s) / oxides. In certain embodiments For example, the metal oxide can be mixed with the resin and / or lubricant in various ways Permutations are mixed. So they can z. For example, all be mixed together at the same time or the lubricant and metal oxide may be mixed with the PTFE resin before mixing be mixed.

The Resin / lubricant / additive mixture can then be preformed z. B. by filling in a cylinder and then pressing under pressure to form a preform. In some embodiments For example, the cylinder may have 50 inches and a pressure of 150 psi used to mix the mixture at ambient temperature in the preform to press. Of course, others can Procedure parameters are also used.

The Preform can then be extruded to tape, z. B. with a piston extruder. In some embodiments, extrusion occurs at a temperature between 80 ° F and 100 ° F and with a rate between 80 and 120 in / min. The final thickness of the tape can between 1 and 100 mils, preferably between 5 and 75 mils and still more preferably between 10 and 40 mils. Naturally Other process parameters can also be used.

To In extrusion, the tape can then be calendered by passing the tape Mix by hot calender rolls leads to the preservation of the band uniformity as well as the evaporation lubricating the lubricant. The calendering can at a Temperature between 300 ° F and 400 ° F and at a Rate between 10 and 20 ft / min. The calender rolls can 20 inches wide and the calender rolls can be one Distance between 10 and 17 mil. Of course you can also other method parameters are used.

To The band can be calendered by clamping into a membrane be formed. During this process, the tape becomes biaxially stretched to form a thin membrane. Preferably the stretching takes place at a speed between 30 ft / min and 80 ft / min. Preferably, the stretching is done several times, even in the same direction. So can, for. B., the band between 1- and 20 times (preferably between 10 and 12 times) in the transverse direction and between 1 and 5 times (preferably 3 times) in the machine direction to be stretched. Different temperatures can be used be, for. B., between 150 ° F and 800 ° F, like, z. At 200 ° F, at 500 ° F, at 650 ° F or at 700 ° F. These temperatures can be increased or otherwise vary with the stretching cycles.

To The membrane may be heat treated to tension to stabilize the microstructure of a membrane. This sintering can in an oven at a temperature between 400 ° F and 750 ° F, preferably between 650 ° F and 750 ° F, for a period of time between 1 and 120 seconds, and preferably between 10 and 30 seconds. The final thickness of the membrane can range between 0.05 and 20 mils (preferably 2 mils).

Examples were according to an exemplary embodiment of the present invention.

Example # 1 was prepared with 3 wt% zinc oxide nanopowder (using the weight of the PTFE resin as the base). The PTFE resin used was Dupont ^Teflon® PTFE 601A and the lubricant was Isopar K. The resulting membranes were compared to the specifications for two PTFE membranes available from GE Energy: QMO8 and QMO11.

example 1

fine DuPont 601A resin powder was used with 20% by weight of Isopar K of a V-mixer at ambient conditions for about 30 minutes mixed. The resin / Isopar mixture was heated at 90 ° F for 24 hours let move in. The retracted PTFE / Isopar mixture was washed with 3 wt .-% zinc oxide nanopowders using a V-mixer for mixed for about 15 minutes. The resin / isopar / zinc oxide was pressurized 150 psi using a billet press in cylindrical form (preform) brought. The preform was at a Temperature of 80 ° F using a piston extruder extruded into a ribbon. The Isopar was removed from the belt by passing of the belt through a series of hot calender rolls at one Temperature of 200 ° F away. The tape was stretched biaxially, to obtain a porous PTFE membrane (twice in the machine direction and stretched eight times in the transverse direction). The microstructure of the PTFE membrane was made by applying heat at a temperature of Stabilized 680 ° F.

The membrane was tested according to product test specifications and compared to commercially available GE standard membrane. It was found that the zinc oxide nanopowder additive had dispersed uniformly within the PTFE matrix and was locked in the microstructure. properties Standard GE membrane z. B .: QMO11 Example # 1: ePTFE / metal oxide composite membrane Unit weight (oz / yd ² ) 0.54 0.68 Thickness (mil) 1 1.2 Bubble point (psi) 19 21 Air flow (cfm) 0.32 0.38 Mullen (without carrier) (psi) 16 21 Mullen (with carrier) (psi) 70 96 Peel strength MD (lbf / in.) XD (lbf / in.) 0.34 0.2 0.54 0.31 Tensile strain (%) MD XD 270 114 220 78 Table 1: Comparison of Example # 1 with specifications for a standard GE membrane (eg QMO11).

tensile strenght and elongation were according to ASTM D5035 and Mullen was applied from ASTM D751-00 Method A, Procedure 1.

Example 2

fine DuPont 603 A resin powder was used with 22% by weight of Isopar M of a V-mixer at ambient conditions for about 20 minutes mixed. The resin / isopar mixture was heated at 110 ° F for 48 hours rest or move in. The retracted PTFE / Isopar mixture was mixed with 7 wt .-% zinc oxide nanopowder using a V-mixer mixed for about 30 minutes. The resin / isopar / zinc oxide was passed through Pressure of 100 psi using a billet press in cylindrical form (preform) brought. The preform was at a Temperature of 110 ° F using a piston extruder extruded into a ribbon. The Isopar was removed from the belt by passing of the belt through a series of hot calender rolls at one Temperature of 250 ° F away. The tape was stretched biaxially, to obtain a porous PTFE membrane (five times in the machine direction and twelve times in the transverse direction stretched). The microstructure of the PTFE membrane was applied by applying stabilized by heat at a temperature of 720 ° F.

The Membrane was made according to product test specifications tested and with a commercially available GE standard membrane compared. It was found that the zinc oxide nanopowder Additive evenly dispersed in the PTFE matrix had and was locked in the microstructure.

All disclosed and claimed numbers and numbers are possible and close at least some variation and deviation one.

While the invention has been described in connection with what is currently for the most practical and preferred embodiment it should be clear that the invention is not disclosed embodiment is limited but on the contrary, various modifications and equivalents To cover arrangements that are within the spirit and scope of the appended claims.

method for preparing a blend used in the manufacture of a polytetrafluoroethylene (PTFE) membrane is used, which includes metal oxide (s). The mixture includes PTFE resin, a lubricant and a metal oxide one. The mixture can be further processed to form a PTFE membrane.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 5697390 [0003]
• US 5827327 [0003]
• US 6120532 [0003]
• US 6270707 [0003]

Claims (18)

Method for producing a polytetrafluoroethylene membrane, comprising metal oxide (s), the process comprising the steps of: (A) Mixing a polytetrafluoroethylene resin having a weight, a lubricant having a weight and a metal oxide, that has a weight, being the weight of the lubricant between 15 and 25 percent of the weight of the polytetrafluoroethylene resin includes, wherein the weight of the metal oxide is up to 10 percent the weight of the polytetrafluoroethylene resin, and wherein the metal oxide at least one dimension of less than 100 nm having; (b) forming a preform comprising a mixture the polytetrafluoroethylene resin, the lubricant and the metal oxide; (C) Extruding the preform to form a tape having a thickness between 1 and 100 mils; (d) calendering the ribbon around the Facilitate evaporation of the lubricant; (e) clamping the Bandes by biaxial stretching in a first direction and in one second direction, which is perpendicular to the first direction, around a To form membrane, and (f) sintering the membrane at a temperature between 400 ° F and 750 ° F for a period of time between 1 and 120 seconds, with the membrane after sintering has a thickness between 0.05 and 20 mils. The method of claim 1, wherein step (a) comprises the steps includes: Mixing the polytetrafluoroethylene resin with the Lubricant in a V-mixer for a period between 1 and 60 minutes to form a resin / lubricant mixture; Move in leave the resin / lubricant mixture for a period of time between 1 and 120 hours, and Mixing the resin / lubricant mixture with the metal oxide in a V-mixer for a period of time between 1 and 60 minutes. The method of claim 1, wherein the lubricant an isoparaffin solvent. The method of claim 2, wherein the metal oxide is titanium dioxide, Zinc oxide, alumina, magnesia, silver oxide or a mixture including thereof. The method of claim 2, wherein the metal oxide is at least has a dimension of less than 50 nm. The method of claim 2, wherein the metal oxide is at least has a dimension of less than 30 nm. The method of claim 2, wherein the metal oxide has a specific surface area greater than 10 m ² / g. The method of claim 2, wherein the metal oxide has a specific surface area greater than 50 m ² / g. The method of claim 2, wherein the metal oxide has a specific surface area greater than 90 m ² / g. Method for introducing a metal oxide into a Mixture comprising a polytetrafluoroethylene resin and a lubricant, the method comprising the steps of: (a) mixing the Polytetrafluoroethylene resin with the lubricant in a V-mixer for a period between 1 and 60 minutes to make a resin / lubricant mixture; (b) retract the Resin / lubricant mixture for a period of time between 1 and 120 hours, and (c) mixing the resin / lubricant mixture with the metal oxide in a V-blender for a period of time between 1 and 60 minutes; wherein a weight of the lubricant between 15 and 25 percent of the weight of the polytetrafluoroethylene resin includes, wherein a weight of the metal oxide up to 10 percent the weight of the polytetrafluoroethylene resin, and wherein the metal oxide at least one dimension of less than 100 nm having; The method of claim 10, wherein step (b) is at a temperature between 40 ° F and 200 ° F takes place. The method of claim 10, wherein the lubricant an isoparaffin solvent. The method of claim 10, wherein the metal oxide comprises zinc oxide, aluminum oxide or silver oxide and has a specific surface area of more than 90 m ² / g and at least a dimension of less than 50 nm. A composition comprising: a polytetrafluoroethylene resin; a lubricant comprising an isoparaffinic solvent and a metal oxide; wherein a weight of the lubricant comprises between 15 and 25 percent of a weight of the polytetrafluoroethylene resin; wherein a weight of the metal oxide comprises up to 10% by weight of the polytetrafluoroethylene resin, and wherein the metal oxide has at least a dimension of less than 100 nm and a specific surface area of more than 50 m ² / g. A composition according to claim 14, wherein the metal oxide Zinc oxide, alumina or silver oxide. A composition according to claim 14, wherein the metal oxide Includes zinc oxide. A composition according to claim 16, wherein the lubricant an isoparaffin solvent. The composition of claim 17, wherein the metal oxide has at least a dimension of less than 50 nm and a specific surface area greater than 90 m ² / g.